Synthesis of CuInS2-ZnS quantum dots for different Cu/In ratios by one-pot method and its applications to white light-emitting diodes

This paper reports one-pot method toward the synthesis of CuInS2/ZnS hybrid nanoparticles. First, CuInS2 quantum dots (QDs) were synthesized in the noncoordinating solvent octadecene using copper chlorine, indium chlorine and dodecanethiol. Copper indium sulfide (CIS) quantum dots (QDs) for different Cu/In molar ratios of 1/1, 1/2, and 1/4 are synthesized. The band gap energy of CIS QDs is observed to be dependent for Cu/In ratio, exhibiting a higher band gap from more Cu-deficient QDs. The emission wavelengths of all CIS QDs belong to a deep red region (710-780 nm) with relatively low quantum yields (QYs) of 3.4-7.8%. Compared to respective original core QDs, the absorption peaks of CIS/ZnS QDs are blue-shifted, and their emission wavelengths move to a higher energy accordingly, showing a quite tunable emission from yellow to red. The effective surface passivation by a ZnS overlayer results in a dramatic increase in QY of CIS/ZnS QDs in the range of 38-48%. Finally, high luminescent CIS/ZnS QDs with high luminescent PL efficiency are used for white light emitting diode.